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VIDEO(4) FreeBSD Kernel Interfaces Manual VIDEO(4) NAME video - device-independent video driver layer SYNOPSIS video* at uvideo? #include <sys/types.h> #include <sys/ioctl.h> #include <sys/videoio.h> DESCRIPTION The video driver provides support for various video devices. It provides a uniform programming interface layer above different underlying video hardware drivers. The video driver uses the V4L2 (Video for Linux Two) API which is widely used by video applications. Therefore this document mainly describes the V4L2 API parts which are supported by the video driver. For security reasons video recording is blanked by default. To achieve this, the video driver blanks image data received from the underlying video hardware driver. The superuser can change this behavior using the kern.video.record sysctl(2) variable: kern.video.record=0 # Recording is blanked (default) kern.video.record=1 # Recording is enabled IOCTLS The following ioctl(2) commands are supported: VIDIOC_QUERYCAP struct v4l2_capability * Query device capabilities. struct v4l2_capability { u_int8_t driver[16]; u_int8_t card[32]; u_int8_t bus_info[32]; u_int32_t version; u_int32_t capabilities; u_int32_t device_caps; u_int32_t reserved[3]; }; VIDIOC_ENUM_FMT struct v4l2_fmtdesc * Enumerate image formats. struct v4l2_fmtdesc { u_int32_t index; u_int32_t type; u_int32_t flags; u_int8_t description[32]; u_int32_t pixelformat; u_int32_t mbus_code; u_int32_t reserved[3]; }; VIDIOC_S_FMT struct v4l2_format * Set the data format. struct v4l2_format { u_int32_t type; union { struct v4l2_pix_format pix; struct v4l2_pix_format_mplane pix_mp; struct v4l2_window win; struct v4l2_vbi_format vbi; struct v4l2_sliced_vbi_format sliced; struct v4l2_sdr_format sdr; struct v4l2_meta_format meta; u_int8_t raw_data[200]; } fmt; }; VIDIOC_G_FMT struct v4l2_format * Get the data format. Same structure as for VIDIOC_S_FMT. VIDIOC_ENUMINPUT struct v4l2_input * Enumerate video inputs. struct v4l2_input { u_int32_t index; u_int8_t name[32]; u_int32_t type; u_int32_t audioset; u_int32_t tuner; v4l2_std_id std; u_int32_t status; u_int32_t capabilities; u_int32_t reserved[3]; }; VIDIOC_G_INPUT int * Get the current video input. VIDIOC_S_INPUT int * Select the current video input. VIDIOC_REQBUFS struct v4l2_requestbuffers * Initiate memory mapping or user pointer I/O. struct v4l2_requestbuffers { u_int32_t count; u_int32_t type; u_int32_t memory; u_int32_t capabilities; u_Int32_t flags; u_int32_t reserved[3]; }; VIDIOC_QUERYBUF struct v4l2_buffer * Query the status of a buffer. struct v4l2_buffer { u_int32_t index; u_int32_t type; u_int32_t bytesused; u_int32_t flags; u_int32_t field; struct timeval timestamp; struct v4l2_timecode timecode; u_int32_t sequence; u_int32_t memory; union { u_int32_t offset; unsigned long userptr; struct v4l2_plane *planes; int32_t fd; } m; u_int32_t length; u_int32_t reserved2; union { int32_t request_fd; u_int32_t reserved; } }; VIDIOC_QBUF struct v4l2_buffer * Add a buffer to the queue. Same structure as for VIDIOC_QUERYBUF. VIDIOC_DQBUF struct v4l2_buffer * Remove a buffer from the queue. Same structure as for VIDIOC_QUERYBUF. VIDIOC_STREAMON int * Start video stream. VIDIOC_STREAMOFF int * Stop video stream. VIDIOC_TRY_FMT struct v4l2_format * Try a data format. Same structure as for VIDIOC_S_FMT. VIDIOC_ENUM_FRAMEINTERVALS struct v4l2_frmivalenum * Enumerate frame intervals. struct v4l2_frmivalenum { u_int32_t index; u_int32_t pixel_format; u_int32_t width; u_int32_t height; u_int32_t type; union { struct v4l2_fract discrete; struct v4l2_frmival_stepwise stepwise; }; u_int32_t reserved[2]; }; struct v4l2_frmival_stepwise { struct v4l2_fract min; struct v4l2_fract max; struct v4l2_fract step; }; VIDIOC_S_PARM struct v4l2_streamparm * Set streaming parameters. struct v4l2_streamparm { u_int32_t type; union { struct v4l2_captureparm capture; struct v4l2_outputparm output; u_int8_t raw_data[200]; } parm; }; struct v4l2_captureparm { u_int32_t capability; u_int32_t capturemode; struct v4l2_fract timeperframe; u_int32_t extendedmode; u_int32_t readbuffers; u_int32_t reserved[4]; }; struct v4l2_outputparm { u_int32_t capability; u_int32_t outputmode; struct v4l2_fract timeperframe; u_int32_t extendedmode; u_int32_t writebuffers; u_int32_t reserved[4]; }; VIDIOC_G_PARM struct v4l2_streamparm * Get the streaming parameters. Same structures as for VIDIOC_S_PARM. VIDIOC_QUERYCTRL struct v4l2_queryctrl * Enumerate control items. struct v4l2_queryctrl { u_int32_t id; u_int32_t type; u_int8_t name[32]; int32_t minimum; int32_t maximum; int32_t step; int32_t default_value; u_int32_t flags; u_int32_t reserved[2]; }; Command independent enumerations are: enum v4l2_buf_type { V4L2_BUF_TYPE_VIDEO_CAPTURE = 1, V4L2_BUF_TYPE_VIDEO_OUTPUT = 2, V4L2_BUF_TYPE_VIDEO_OVERLAY = 3, V4L2_BUF_TYPE_VBI_CAPTURE = 4, V4L2_BUF_TYPE_VBI_OUTPUT = 5, V4L2_BUF_TYPE_SLICED_VBI_CAPTURE = 6, V4L2_BUF_TYPE_SLICED_VBI_OUTPUT = 7, V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY = 8, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE = 9, V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE = 10, V4L2_BUF_TYPE_SDR_CAPTURE = 11, V4L2_BUF_TYPE_SDR_OUTPUT = 12, V4L2_BUF_TYPE_META_CAPTURE = 13, V4L2_BUF_TYPE_META_OUTPUT = 14, /* Deprecated, do not use */ V4L2_BUF_TYPE_PRIVATE = 0x80, }; enum v4l2_memory { V4L2_MEMORY_MMAP = 1, V4L2_MEMORY_USERPTR = 2, V4L2_MEMORY_OVERLAY = 3, V4L2_MEMORY_DMABUF = 4, }; enum v4l2_ctrl_type { V4L2_CTRL_TYPE_INTEGER = 1, V4L2_CTRL_TYPE_BOOLEAN = 2, V4L2_CTRL_TYPE_MENU = 3, V4L2_CTRL_TYPE_BUTTON = 4, V4L2_CTRL_TYPE_INTEGER64 = 5, V4L2_CTRL_TYPE_CTRL_CLASS = 6, V4L2_CTRL_TYPE_STRING = 7, V4L2_CTRL_TYPE_BITMASK = 8, V4L2_CTRL_TYPE_INTEGER_MENU = 9, V4L2_CTRL_COMPOUND_TYPES = 0x0100, V4L2_CTRL_TYPE_U8 = 0x0100, V4L2_CTRL_TYPE_U16 = 0x0101, V4L2_CTRL_TYPE_U32 = 0x0102, V4L2_CTRL_TYPE_AREA = 0x0106, /* Compound types are >= 0x0100 */ V4L2_CTRL_TYPE_HDR10_CLL_INFO = 0x0110, V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY = 0x0111, V4L2_CTRL_TYPE_H264_SPS = 0x0200, V4L2_CTRL_TYPE_H264_PPS = 0x0201, V4L2_CTRL_TYPE_H264_SCALING_MATRIX = 0x0202, V4L2_CTRL_TYPE_H264_SLICE_PARAMS = 0x0203, V4L2_CTRL_TYPE_H264_DECODE_PARAMS = 0x0204, V4L2_CTRL_TYPE_H264_PRED_WEIGHTS = 0x0205, V4L2_CTRL_TYPE_FWHT_PARAMS = 0x0220, V4L2_CTRL_TYPE_VP8_FRAME = 0x0240, V4L2_CTRL_TYPE_MPEG2_QUANTISATION = 0x0250, V4L2_CTRL_TYPE_MPEG2_SEQUENCE = 0x0251, V4L2_CTRL_TYPE_MPEG2_PICTURE = 0x0252, V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR = 0x0260, V4L2_CTRL_TYPE_VP9_FRAME = 0x0261, V4L2_CTRL_TYPE_HEVC_SPS = 0x0270, V4L2_CTRL_TYPE_HEVC_PPS = 0x0271, V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS = 0x0272, V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX = 0x0273, V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS = 0x0274, V4L2_CTRL_TYPE_AV1_SEQUENCE = 0x280, V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY = 0x281, V4L2_CTRL_TYPE_AV1_FRAME = 0x282, V4L2_CTRL_TYPE_AV1_FILM_GRAIN = 0x283, }; enum v4l2_frmivaltypes { V4L2_FRMIVAL_TYPE_DISCRETE = 1, V4L2_FRMIVAL_TYPE_CONTINUOUS = 2, V4L2_FRMIVAL_TYPE_STEPWISE = 3, }; Command independent structures are: struct v4l2_pix_format { u_int32_t width; u_int32_t height; u_int32_t pixelformat; u_int32_t field; u_int32_t bytesperline; u_int32_t sizeimage; u_int32_t colorspace; u_int32_t priv; u_int32_t flags; union { u_int32_t ycbcr_enc; u_int32_t hsv_enc; }; u_int32_t quantization; u_int32_t xfer_func; }; struct v4l2_window { struct v4l2_rect w; u_int32_t field; u_int32_t chromakey; struct v4l2_clip *clips; u_int32_t clipcount; void __user *bitmap; u_int8_t global_alpha; }; struct v4l2_vbi_format { u_int32_t sampling_rate; u_int32_t offset; u_int32_t samples_per_line; u_int32_t sample_format; int32_t start[2]; u_int32_t count[2]; u_int32_t flags; u_int32_t reserved[2]; }; struct v4l2_sliced_vbi_format { u_int16_t service_set; u_int16_t service_lines[2][24]; u_int32_t io_size; u_int32_t reserved[2]; }; struct v4l2_fract { u_int32_t numerator; u_int32_t denominator; }; Command independent typedefs are: typedef u_int64_t v4l2_std_id; READ Video data can be accessed via the read(2) system call. The main iteration for userland applications occurs as follow: 1. Open /dev/video* via the open(2) system call. 2. Read video data from the device via the read(2) system call. The video stream will be started automatically with the first read, which means there is no need to issue a VIDIOC_STREAMON command. The read will always return a consistent video frame, if no error occurs. 3. Process video data and start over again with step 2. 4. When finished, stop the video stream via the close(2) system call. The select(2), poll(2) and kqueue(2) system calls are supported for this access type. They will signal when a frame is ready for reading without blocking. MMAP Video data can be accessed via the mmap(2) system call. The main iteration for userland applications occurs as follow: 1. Open /dev/video* via the open(2) system call. 2. Request desired number of buffers via the VIDIOC_REQBUFS ioctl command. The maximum number of available buffers is normally limited by the hardware driver. 3. Get the length and offset for the previously requested buffers via the VIDIOC_QUERYBUF ioctl command and map the buffers via the mmap(2) system call. 4. Initially queue the buffers via the VIDIOC_QBUF ioctl command. 5. Start the video stream via the VIDIOC_STREAMON ioctl command. 6. Dequeue one buffer via the VIDIOC_DQBUF ioctl command. If the queue is empty, the ioctl will block until a buffer gets queued or an error occurs (e.g. a timeout). 7. Process video data. 8. Requeue the buffer via the VIDIOC_QBUF ioctl command and start over again with step 6. 9. When finished, stop the video stream via the VIDIOC_STREAMOFF ioctl command. The select(2), poll(2) and kqueue(2) system calls are supported for this access type. They will signal when at least one frame is ready for dequeuing, allowing to call the VIDIOC_DQBUF ioctl command without blocking. FILES /dev/video SEE ALSO video(1), ioctl(2), uvideo(4) HISTORY The video driver first appeared in OpenBSD 4.4. FreeBSD 14.1-RELEASE-p8 January 15, 2025 FreeBSD 14.1-RELEASE-p8